Patterns of extinction and recovery of phacopid trilobites during the Frasnian–Famennian (Late Devonian) mass extinction event, Canning Basin, Western Australia

2008 ◽  
Vol 146 (1) ◽  
pp. 12-33 ◽  
Author(s):  
RAIMUND FEIST ◽  
KENNETH J. MCNAMARA ◽  
CATHERINE CRÔNIER ◽  
RUDY LEROSEY-AUBRIL
Keyword(s):  
Shallow Water ◽  
Western Australia ◽  
Mass Extinction ◽  
New Genus ◽  
Late Devonian ◽  
Canning Basin ◽  
Eye Size ◽  
Extinction Event ◽  
Mass Extinction Event ◽  
First Time

AbstractA diverse fauna of phacopid trilobites is described from the Late Devonian (middle Frasnian to early Famennian) of the northern Canning Basin, Western Australia. One new genus and four species in two genera are described from zones 11, 13a and 13b of the middle and late Frasnian: Trimerocephaloides sinevisus gen. nov. and sp. nov., T. ? linguiformis sp. nov., Acuticryphops acuticeps (Kayser, 1889) and A. klapperi sp. nov. Late Frasnian phacopines are either blind, as shown for the first time in Trimerocephaloides sinevisus, or show trends to decreasing eye size up to the Frasnian–Famennian ‘Kellwasser’ mass extinction event. This evolutionary trend in Acuticryphops is demonstrated to have been global at this time. One new genus and six species of early Famennian phacopids are described, from the Upper triangularis, crepida and rhomboidea zones: Houseops gen. nov. with the new taxa H. canningensis sp. nov., H. beckeri sp. nov. and H. sp. A, Babinops planiventer Feist & Becker, 1997, B. minor sp. nov., Trimerocephalus tardispinosus Feist & Becker, 1997 and T. mimbi sp. nov. In contrast to European sections where exclusively blind phacopids are known in earliest Famennian sites, initial recovery following the mass extinction event in Canning peri-reefal environments is characterized by oculated forms. These trilobites must have evolved from conservative ancestors with normal eyes that had succeeded in surviving the Kellwasser biocrises in reef-related shallow water niches. Thus the origin of post-event phacopids from shallow water environments is demonstrated for the first time. Descendant lineages show increasing eye size, increased cephalic vaulting and effacement during the early Famennian.

scholarly journals Dinosaurs in decline tens of millions of years before their final extinction

2016 ◽  
Vol 113 (18) ◽  
pp. 5036-5040 ◽  
Author(s):  
Manabu Sakamoto ◽  
Michael J. Benton ◽  
Chris Venditti
Keyword(s):  
Mass Extinction ◽  
Marked Reduction ◽  
Evolutionary Dynamics ◽  
General Pattern ◽  
Extinction Rate ◽  
Catastrophic Event ◽  
Extinction Event ◽  
Mass Extinction Event ◽  
First Time

Whether dinosaurs were in a long-term decline or whether they were reigning strong right up to their final disappearance at the Cretaceous–Paleogene (K-Pg) mass extinction event 66 Mya has been debated for decades with no clear resolution. The dispute has continued unresolved because of a lack of statistical rigor and appropriate evolutionary framework. Here, for the first time to our knowledge, we apply a Bayesian phylogenetic approach to model the evolutionary dynamics of speciation and extinction through time in Mesozoic dinosaurs, properly taking account of previously ignored statistical violations. We find overwhelming support for a long-term decline across all dinosaurs and within all three dinosaurian subclades (Ornithischia, Sauropodomorpha, and Theropoda), where speciation rate slowed down through time and was ultimately exceeded by extinction rate tens of millions of years before the K-Pg boundary. The only exceptions to this general pattern are the morphologically specialized herbivores, the Hadrosauriformes and Ceratopsidae, which show rapid species proliferations throughout the Late Cretaceous instead. Our results highlight that, despite some heterogeneity in speciation dynamics, dinosaurs showed a marked reduction in their ability to replace extinct species with new ones, making them vulnerable to extinction and unable to respond quickly to and recover from the final catastrophic event.

Paleocene diversification of bucciniform gastropods on Seymour Island, Antarctica

1996 ◽  
Vol 70 (6) ◽  
pp. 923-934 ◽  
Author(s):  
Anton E. Oleinik ◽  
William J. Zinsmeister
Keyword(s):  
New Species ◽  
Mass Extinction ◽  
Fossil Record ◽  
New Genus ◽  
Shell Morphology ◽  
Geographic Isolation ◽  
Extinction Event ◽  
Early Paleocene ◽  
Mass Extinction Event ◽  
Seymour Island

Following the mass extinction event at the end of the Cretaceous, the marine molluscan faunas of the high southern latitudes underwent a marked period of diversification during the early Paleocene. The appearance of four new species belonging to the new genus Seymourosphaera, tentatively placed in the subfamily Pseudolivinae, from the lower Paleocene strata of Seymour Island, Antarctic Peninsula, clearly illustrates the post-Cretaceous extinction diversification. The abrupt radiation of the buccinids during the early Paleocene, was also apparently related to geographic isolation of Antarctica during final breakup of Gondwana. Comparative analysis of shell morphology of Seymourosphaera, new genus reveals close morphologic similarities, not only with taxa within Pseudolivinae, but also with several genera and subgenera belonging to the families Buccinidae and Nassariidae. However, incompleteness of the fossil record and a “generalized” shell morphology make difficult establishment of unequivocal phylogenetic relationships for Seymourosphaera. A taxonomic review of most closely related, and possibly ancestral genus Austrosphaera Camacho, 1949, is provided. The following new species of genus Seymourosphaera new genus are described: Seymourosphaera bulloides new species, S. subglobosa new species, S. depressa new species, and S. elevata new species.

Revision of Cyclida (Pancrustacea, Multicrustacea), with five new genera

2020 ◽  
Vol 296 (3) ◽  
pp. 245-303
Author(s):  
Carrie E. Schweitzer ◽  
Eduard V. Mychko ◽  
Rodney M. Feldmann
Keyword(s):  
Mass Extinction ◽  
New Genus ◽  
New Combinations ◽  
New Genera ◽  
Extinction Event ◽  
Mass Extinction Event ◽  
Permian Mass Extinction ◽  
Freshwater Environments

All cyclidan species represented by existing material are illustrated photographically. New genera within Cyclidae include Ambocyclus new genus; Carabicyclus new genus; Chernyshevine new genus, Litocyclus new genus; and Tazawacyclus new genus with the following new combinations: A. capidulum (Chernyschev, 1933); A. simulans (Reed, 1908); A. ? minutus (Rogers, 1902); Carabicyclus wrighti (Woodward, 1870); L. bilobatus (Woodward, 1870); L. ? communis (Rogers, 1902); L. jonesianus (Woodward, 1870); L. ? permarginatus (Rogers, 1902); L. torosus (Woodward, 1870); Chernyshevine spinosus (Chernyschev, 1933); T. tazawai (Niko & Ibaraki, 2011); U. harknessi (Woodward, 1870); and U. woodwardi (Reed, 1893). New genera within Americlidae include Brittaniclus and Dziklus with the following new combinations: B. rankini (Woodward, 1868); B. scotti (Woodward, 1894); B. testudo (Peach, 1882); and D. obesus (Schram, Vonk & Hof, 1997). A neotype is herein designated for Halicyne plana. Each family within Cyclida occupies a distinct morphospace. Two families survived the end-Permian mass extinction event. Most cyclidans occupied marine conditions, but some are known from marginal marine and freshwater environments.

Astronomical calibration of paleoclimatic and planktic foraminiferal events of the Cretaceous-Paleogene transition at Zumaia, Spain

2021 ◽  
Author(s):  
Vicente Gilabert ◽  
Sietske J. Batenburg ◽  
Ignacio Arenillas ◽  
José A. Arz
Keyword(s):  
Mass Extinction ◽  
Deccan Traps ◽  
Deccan Volcanism ◽  
Extinction Event ◽  
First Occurrence ◽  
Mass Extinction Event ◽  
Environmental Events ◽  
Chicxulub Impact ◽  
First Time ◽  
Intense Debate

<p>The main trigger for the Cretaceous/Paleogene boundary (KPB) mass extinction is still subject of intense debate. The co-occurrence of the Chicxulub impact (Yucatan, Mexico) and massive Deccan Traps volcanism (India) during Chron C29r hinders disentangling their climatic and environmental effects. Unravelling the influence of Deccan volcanism on the KPB extinction and other Maastrichtian and Danian perturbations requires more accurate age calibrations and duration estimates of biotic and climatic events. Here we integrate existing astrochronologies of the Zumaia section, allowing us to produce a refined cyclostratigraphic calibration of the main planktic foraminiferal and paleoclimatic events recorded across the KPB in the well-know Zumaia section (NW, Spain).</p><p>At Zumaia, the KPB is marked by a ~8 cm-thick dark clay bed, with low values of %CaCO<sub>3</sub> and δ<sup>13</sup>C. The Chicxulub ejecta-rich airfall layer has been identified at the base of the dark clay bed, but it is partially masked within a 1–2 cm-thick diagenetic calcitic layer. At Zumaia, the KPB has been astronomically calibrated at 66 Ma (compatible with radioisotopic ages), and the duration of dark clay bed is estimated at ~10 kyr. The first appearances (FA) of the Danian planktic foraminiferal index-species <em>Parvularugoglobigerina longiapertura</em>, <em>Parvularugoglobigerina eugubina</em>, <em>Eoglobigerina simplicissima</em>, <em>Parasubbotina pseudobulloides</em>, <em>Subbotina triloculinoides</em> and <em>Globanomalina compressa</em> have been orbitally tuned at Zumaia, to have occurred at 8, 30, 45, 70, 210, and 475 kyr after the KPB. Specimens of <em>Plummerita hantkeninoides</em> have been identified for the first time in the Maastrichtian of Zumaia, and its first occurrence is dated at ~100 kyr before the KPB. Based on d<sup>13</sup>C data, we have identified the late Maastrichtian Warming Event (LMWE), the early Danian Dan-C2 and the Lower-C29N events. Additionally, a bloom of the eutrophic/opportunist genus <em>Chiloguembelitria</em>, interpreted as a period of environmental stress, has also been recognized above and separate from the KPB clay bed. Besides the KPB, the main paleoclimatic/paleoenvironmental events have been astronomically calibrated at Zumaia as follows: the LMWE between 270 and 120 kyr before the KPB, the Dan-C2 event between 205 and 305 kyr after the KPB, the Lower-C29N event between 520 and 595 kyr after the KPB, and the Chiloguembelitria bloom between 100 and 305 kyr after the KPB. According to this chronology, we conclude that the LMWE and early Danian <em>Chiloguembelitria</em> bloom seems to coincide in time with major volcanic pulses of the Deccan Traps, unlike the Dan-C2 and Lower-C29N events, which appear to have been driven by orbital forcing. Regardless of the cause of climatic and environmental events, all these perturbations appear unrelated to the KPB mass extinction event. It supports the hypothesis that the influence of Deccan volcanism on planktic foraminiferal assemblages during the Maastrichtian and Danian was limited.</p>

scholarly journals Timing and pacing of the Late Devonian mass extinction event regulated by eccentricity and obliquity

2017 ◽  
Vol 8 (1) ◽  
Author(s):  
David De Vleeschouwer ◽  
Anne-Christine Da Silva ◽  
Matthias Sinnesael ◽  
Daizhao Chen ◽  
James E. Day ◽  
...  
Keyword(s):  
Mass Extinction ◽  
Late Devonian ◽  
Extinction Event ◽  
Mass Extinction Event

scholarly journals Divergence rates of subviral pathogens of angiosperms abruptly decreased at the Cretaceous-Paleogene boundary

2019 ◽  
Vol 4 ◽  
pp. 89-101 ◽  
Author(s):  
Piotr Bajdek
Keyword(s):  
Mass Extinction ◽  
Continental Drift ◽  
Time Calibration ◽  
Extinction Event ◽  
Drift Theory ◽  
History Of ◽  
Probable Impact ◽  
Mass Extinction Event ◽  
Extinction Events ◽  
First Time

Biogeographic distribution of infected plants and the continental drift theory allow a tentative time calibration of the phylogenetic tree of Pospiviroidae. Hypothetically, viroids evolved in the late Early Cretaceous shortly after the appearance of angiosperms, which constitute their only known hosts. No decline in the estimated divergence rates of Pospiviroidae is observed during the Late Cretaceous but it appears that they abruptly decreased at the Cretaceous-Paleogene boundary. However, an adaptive radiation of Pospiviroidae which occurred in the late Paleocene may reflect a recovery from the Cretaceous-Paleogene (K–Pg) mass extinction. It seems that the evolutionary history of viroids has been in part shaped by radiation and extinction events of angiosperms. Herein, for the first time I show the probable impact of a mass extinction event on the divergence rates of subviral pathogens, which are the simplest known “lifeforms”.

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